Field of the Invention
The present invention applies to a device comprising a lateral front suspension arm for supporting and steering a wheel and to a steering control device associated thereto, especially for a motorcycle front wheel carried by at least one support arm connected at its upper end to a suspension and/or shock-absorbing block the external movable rod of which is articulated at its end on a front peak of the chassis of a motorcycle.
It has already been proposed to produce a motorcycle front suspension comprising a single support arm of the front wheel which is mounted cantilevered on this arm and wherein a suspension spring is interposed between a front peak of the motorcycle chassis and the support arm by means of a movable rod of a suspension arm which is pivotally mounted on this peak. These motorcycle suspensions of the Mac Pherson type give rise to a problem regarding the connection between the steering handlebar and the single support arm of the front wheel.
In order to ensure the connection between the single support arm and the handlebar, it has been proposed to use a universal joint transmission by links that has revealed relatively expensive and complicated to manufacture, while nevertheless transmitting to the handlebar the sudden reactions due to the displacements of the suspension. Another solution consists in interlocking at least for translational motion the end of the movable rod to the handlebar and in interlocking for rotational motion through a sliding connection this rod to the telescopic suspension block body, this body being rigidly fixed to the single suspension arm. This apparently satisfactory solution has revealed in practice to be very difficult to carry out since there exists no telescopic suspension and shock-absorbing block the rod of which is interlocked in rotational motion with the block body; indeed, such an arrangement would require a sleeve integral with the rod and surrounds the block body while being coupled thereto for rotational motion by grooves, so as not to disturb the hydraulic liquid sealing means of the shock absorber.
One particular object of the present invention is to propose a device comprising a single lateral suspension arm and steering control means adapted to this Mac Pherson type suspension, which are a simple in design, do not transmit stray reactions to the handlebar while allowing to use for the constructing suspension and shock-absorbing block commercially available elements of which the reliability and economy are well established.
With this purpose in view, the suspension spring and/or shock absorbing block is a helical spring of which at least one of the end bearing planes comprises a low friction abutment allowing the spring to rotate freely about its longitudinal axis during its displacements and the steering control means is constituted by a handlebar or wheel rotatively mounted on a vertical axis of the said peak rotatively mounted on an axis substantially perpendicular to the median plane of the front wheel, i.e. to the steering plane, at the upper end of at least one upper link inclined towards the front of the motorcycle from its upper end and the lower end of which is also mounted on the lateral arm or support arm for rotation about an axis substantially perpendicular to the said steering plane at the upper end of at least one lower link inclined towards the front of the motorcycle from its lower end which is rotationally connected to an axis substantially perpendicular to the said steering plane, so that the upper and lower links connected in rotation respectively to the handlebar and to the support arm are pivotally interconnected in a scissor-like manner during the displacements of the front wheel suspension of the motorcycle.
According to the most current embodiment, the upper link and the lower link present substantially the same length and their respective median lines each form, in maximal extension position of the suspension block, an angle of about 30.degree. with the longitudinal axis of this suspension block.
The upper link and the lower link can present substantially different lengths and their respective median lines thus form, in maximal extension position of the suspension block, an angle smaller than 30.degree. with the longitudinal axis of this suspension block. The upper link can also present a length substantially smaller than that of the lower link so as to increase the distance between the front wheel and the axis of articulation interconnecting between the two links. The axis of articulation of the upper link is preferably substantially coaxial to the axis of articulation of the external movable rod of the suspension and shock absorbing block on the front peak of the chassis of the motorcycle.
According to another very compact embodiment of the invention, the upper link presents, on its upper part, a fork with two legs, each of which is rotationally connected to a boss of an arm of the handlebar and has at its lower part, a single central bearing through which extends a pin or assembly shaft and which is disposed between two bearings that are also crossed through by the assembling pin and which are both provided at each of the ends of the legs of a fork of the lower link, two lower legs of which extend therefrom are rotationally connected each to a corresponding boss provided on the support arm. The corresponding upper and lower links present the general form of a trapezium the large base of which is articulated respectively to the handlebar and to the support arm of the front wheel, and the small bases of which are joined to each other in the zone crossed through by the assembly pin and are articulated or hinged to each other.
According to another embodiment of the invention, the rotation connection of the upper end of the upper link and that of the lower end of the lower link are located beyond the bearing planes of the ends of a helical spring constituting the suspension spring of the suspension block. The steering links thus constitute supplementary guiding means of the suspension block during its displacements.
According to a second embodiment, the present invention also relates to a control device for steering a wheel, especially a front wheel of a motorcycle, comprising a handlebar or steering wheel rotatively mounted upon an axle of a frame peak and upon which is mounted rotatively about an upper link substantially perpendicular to the median plane of the front wheel, the upper end of at least one downwardly inclined upper link the lower end of which is articulated to the upper end of at least one lower link upwardly inclined from its lower end which is rotatively mounted on a lower link axle integral with at least one wheel support arm and substantially perpendicular to the median plane of the front wheel, so that the upper and lower links rotatively connected to the handlebar and the support arm, respectively, are interconnected scissor-like to each other during displacement of the front suspension of the motorcycle.
It has already been proposed to connect the handlebar to the lateral arm through a set of links hingedly connected to one another in a scissorlike manner in order to absorb the displacement of the suspension and to transmit to the wheel support arm and to the wheel the torques exerted upon the handlebar. This solution has revealed satisfactory when the upper and lower axes of articulation of the respective upper and lower links substantially intersect the longitudinal axis of the suspension helical spring. On the contrary, when it has been envisaged to reduce the height requirement of this type of single arm suspension by shifting the axis of articulation of the suspension spring with respect to the axis of orientation of the support arm, and by shifting in a similar way the lower axis of articulation of the lower link, for example in order to house the steering articulation of a steering arm of the wheel support arm, jamming and "hard point" phenomena have appeared in the articulations of the links.
The aim of the present invention is to provide a steering control device that is adapted to this more compact type of suspension and steering control and which has a simple design and does not transmit interference reactions to the handlebar while yet limiting the displacement zone of the links and the volume of fairing that covers it.
With this purpose in view, the articulation between the lower end of the upper link and the upper end of the lower link is constituted by a ball-and-socket articulation adapted to absorb the relative decentering of the upper and lower link axes during the rotation of the handlebar.
According to another embodiment of the invention, the center line of the upper link substantially intersects the longitudinal axis of the helical suspension spring corresponding to the said wheel.
Due to the disposition of the links according to the invention, the lower link axle can be placed on the opposite side of the motorcycle frame, with respect to the orientation axis of the wheel support arm and to the longitudinal axis of the suspension spring and the lower articulation of a helical suspension spring corresponding to the wheel can be connected to the wheel support arm on the side of the motorcycle frame with respect to the orientation axis of the wheel support arm.
According to one embodiment of the invention, the center line of the upper link axis substantially intersects the longitudinal axis of the helical suspension spring associated to said wheel.
Due to the arrangement of the links in accordance with the invention it is possible to place the lower link axis on the opposite side of the motorcycle chassis with respect to the steering axis of the wheel support arm and the longitudinal axis of the suspension spring, and the lower articulation of a helical suspension spring associated to the wheel can be connected to do wheel support arm on the side of the motorcycle chassis with respect to the axis of orientation of the wheel support arm.
According to a further embodiment of the invention, the lower link is shorter than the upper link and is adapted to move towards a position substantially perpendicular to the axis of orientation of the wheel support arm under conditions of the maximum compression of the suspension of the wheel.
The upper part of the ball-and-socket articulation is advantageously constituted by a sphere-receiving carter secured to the lower end of the upper link, and its lower part is constituted by a ball bearing sphere adjustably secured to the upper end of the lower link.